Intervertebral implants may be used as spacers for two adjacent bodies of vertebrae in the case of a defective intervertebral disk. The distance between the bodies of vertebrae, reduced by the defective intervertebral disc, can be enlarged by such an implant so that the stress on joints is relieved.
A generic, intervertebral prosthesis is known from the International Publication WO 03/015645 to MATHIEU. This known intervertebral prosthesis comprises a middle piece, which is introduced into the intervertebral space and from which a pair of longitudinal appendices protrude cranially and caudally to the right and to the left of the middle piece so that the middle piece can be held in place by means of the appendices between the processi spinosi of two adjacent bodies of vertebrae. This known prosthesis comprises a middle part which cannot be expanded, so that an extended position of the adjacent bodies of the vertebrae cannot be produced by the prosthesis itself.
International Publication WO 98/46173 to SCHÄR discloses a vertebral prosthesis which can be telescoped by means of a ratchet mechanism. However, this prosthesis must be introduced into the intervertebral space making it necessary to remove the defective intervertebral disc.